Why I (M20) can’t get a boner?

Hello guys, so I (M20) have been talking to this girl (F20) since January, met her through Instagram and clicked straight away. For context, I’ve never had a girlfriend or sex and I have social anxiety and overall I’m kind of awkard. The thing is that we clicked and basically chatted all day every day, I saw her in person in August (Yes I know… I just was kind of scared I could fuck it up in person and evaded meeting but I finally did) We have been seeing each other a few times a week and spending time with each other. We have kissed and basically touched it other everywhere. The thing is that when we are kissing and touching I can’t get a hard on, its flaccid all the way at first I thought mmh maybe is nerves, but today I went again to her place and we grinded with just boxers and yeah dont get me wrong it felt nice she was on top of me doing it but still, I just could get a hard on, like not at all, it was a bit stronger but still flaccid. Happened like 2 hours ago aprox. I told her and she undestood, it was ok and normal. But Im just worried, why cant it get a boner? Do I have ED? Is this normal? Im actually sad and worries dont want this to continue, she told me we can go slower but i dont feel nerves kissing and such but still i cant get my friend to hype up lmao. So yeah basically this is me asking for advice and comfort.